Access name of .rmd file and use in R

Question

I am knitting a markdown file called MyFile.rmd. How can I access the string MyFile during the knitting and use it for:

• use in the title section of the YAML header?

• use in subsequent R chunk?

  ---
  title: "`r rmarkdown::metadata$title`"
  author: "My Name"
  date: "10. Mai 2015"
  output: beamer_presentation
  ---
  
  ## Slide 1
  
  ```{r}
  
  rmarkdown::metadata$title
  
  ```
  

leads to...

... which is incorrect as the file I am knitting is named differently.

> sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-apple-darwin13.4.0 (64-bit)

locale:
[1] de_DE.UTF-8/de_DE.UTF-8/de_DE.UTF-8/C/de_DE.UTF-8/de_DE.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] digest_0.6.8    htmltools_0.2.6 rmarkdown_0.5.1 tools_3.1.2     yaml_2.1.13

Answer 1

rmarkdown::metadata gives you the list of the meta data of the R Markdown, e.g. rmarkdown::metadata$title will be the title of your document. An example:

---
title: "Beamer Presentation Title"
author: "My Name"
date: "10\. Mai 2015"
output: beamer_presentation
---

## Slide 1

Print the title in a code chunk.

```{r}
rmarkdown::metadata$title
```

## Slide 2

The title of the document is `r rmarkdown::metadata$title`.

To obtain the filename of the input document, use knitr::current_input().

Answer 2

You could use the yaml library, like so:

library(yaml)

# Read in the lines of your file
lines <- readLines("MyFile.rmd")
# Find the header portion contained between the --- lines. 
header_line_nums <- which(lines == "---") + c(1, -1)
# Create a string of just that header portion
header <- paste(lines[seq(header_line_nums[1], 
                          header_line_nums[2])], 
                collapse = "\n")
# parse it as yaml, which returns a list of property values
yaml.load(header)

If you save the list returned by yaml.load, you can use it in various chunks as needed. To get the title, you can do this:

properties <- yaml.load(header)
properties$title